Time delay system



Jilly 1, 1959 J. v. PERRONE P 3, 5

TIME DELAY SYSTEM Filed May 31, 1967 INVENTOR. Jmss V. Pemzous MLSON, SETTLE, firm 5m Rh l. 59

United States Patent O 3,452,579 TIME DELAY SYSTEM James V. Perrone, 41 Shady Hollow, Dearborn, Mich. 48124 Continuation-impart of application Ser. No. 574,463, Aug. 23, 1966. This application May 31, 1967, Ser.

Int. Cl. B21d 22/20 US. Cl. 72351 6 Claims ABSTRACT OF THE DISCLOSURE Cross-reference to related application.

This application is a continuation-in-part of my copending application Ser. No. 574,463, filed Aug. 23, 1966, now US. Pat. No. 3,362,207.

Background of the invention The present invention relates generally to a die pad control mechanism for a ram-type press and more particularly to an improved control system for controlling the movement of a die pad between retracted and extended positions.

In modern high speed presses, commonly utilized for performing stamping, drawing or other operations upon sheet metal, it is necessary to provide for accurately controlled movement of the die pad normally carrying the lower of the two cooperating die elements of the press. One type of control movement which has been suggested is to mount the die pad upon one or more individual hydraulically actuated cylinder and piston assemblies and control of the fluid flow to and from the hydraulic actuated cylinders. Thus, upon actuation of the press to its closed or working position, the pistons are forced downwardly by direct contact with the die pad to subject the hydraulic fluid trapped in the piston beneath the piston to a pressure proportional to the working pressure of the press. Upon venting of this hydraulic pressure in a controlled manner, the consequent downward displacement of the die pad during the working stroke is accommodated. Upon opening of the press, i.e. usually vertical retraction of the upper die member, the hydraulic fluid is fed back into the cylinder beneath the piston to elevate the die pad and its member to its neutral position for a subsequent working stroke of the press.

During this cycling operation, it is desirable to delay elevation of the die pad to its original or extended position to allow or aid in stripping complex or deeply drawn parts from the press dies. Several prior art valving assemblies have been proposed for controlling the movement of the die pad during the working stroke of the press and during the return of the die pad to its extended position.

Summary of the invention The present invention is directed to a mechanical control system which provides a time delay in the return of the piston or pistons moving the die pad to its initial extended position. The control system for a ram-type press movable between open and closed positions and a die pad which engages the work and is retracted upon closing of the press ram, includes hydraulic means having a hydraulic actuated piston slidable in a cylinder that is hydraulically 3,452,579 Patented July 1, 1969 connected to an accumulator. A first unidirectional flow path connects the accumulator to .the cylinder which allows restricted flow from the cylinder to the accumulator while a second flow path has normally closed control means to block the flow in the second path. Means are provided for delaying opening of the control means after the press has moved to the closed position which includes a fluid pressure source, a conduit connecting the source to the control means with a valve in the conduit responsive to movement of the die pad to open the valve and place the source in communication with the conduit and time delaying means in the conduit which is opened in response to a predetermined pressure to open the control means and thereby allow the hydraulic fluid to move the die pad to its extended position.

The primary object of the present invention is to provide an improved control valve assembly to control the movement of a die pad in a press.

Another object is to provide a control mechanism which includes a mechanical delaying mechanism that delays the return of the die pad to its extended position after the press is returned to its neutral position.

A further object is to provide a mechanical delay mechanism for the die pad of a ram-type press which is actuated in response to the fluid flow in the mechanism.

A further object is to provide a mechanical delaying mechanism for actuating a control member disposed in a hydraulic flow path between the die pad of a ram-type press and an accumulator.

Other objects and features of the invention will become apparent when considered in conjunction with the following specification and the accompanying drawings.

As shown on the drawings The single figure of the drawings is a sectional View, partly in schematic form, of a hydraulic control system for a ram-type press having the delaying mechanism of the invention incorporated therein.

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that phraseology and terminology employed herein is for the purpose of description and not of limitation.

The valve assembly 10 regulates the flow of hydraulic fluid between a cylinder 12 and an accumulator or tank 14 which are connected to the valve assemblies respectively by lines 16 and 18. During the work stroke of the press ram 20, the piston 22 moves with the press die, and the hydraulic fluid in the cylinder 12 beneath the piston 22 serves as a cushion to protect the die pad as the press ram closes or descends.

During the work stroke of the press ram, hydraulic fluid is supplied from the cylinder 12 through line 16 to the valve body 10 where the fluid passes through a first flow path 24 at a controlled rate to the line 18 and then the accumulator 14. On the return stroke of the press ram, hydraulic fluid is transferred from the accumulator 14 through line 18, and a second flow path 26 in valve body 10 and line 16 to the cylinder 12 to return the piston and the die pad 21 to its extended position ready for the next work cycle.

As disclosed in and claimed in the above-mentioned copending application Ser. No. 574,463, the first flow path 24 includes a variable discharge relief valve 28 for providing a cushioning action during the work stroke of the press and limiting the flow in the first path to unidirectional restricted flow from the cylinder 12 to the accumulator 14. Also, the second flow path 26 between the cylinder 12 and accumulator 14 allows substantially unrestricted flow in either direction but is normally blocked by control means or an actuator 30. As disclosed in my copending application, the actuator 26 includes a valve body 32 normally spring biased to a closed position by spring 34 to block the flow in the second flow path 26. For a detailed description and operation of the variable discharge relief valve 28 and the actuator 30, reference may be had to the above-mentioned copending application which is incorporated herein by reference.

Briefly stated, the valve assembly includes a variable discharge relief valve for controlling the flow of hydraulic fluid during the work stroke of the ram and for providing delayed return of the die pad to its extended position by delayed opening of an unrestricted flow path from the accumulator to the cylinder. The control means or valve 30 is normally closed by the action of the spring 34 and is adapted to be opened a predetermined period after the press type ram has been returned to its neutral position. This time is required to allow removal of the work pieces from between the die elements and initial positioning of the next subsequent work piece between the die members.

According to this invention, means are provided for delaying the return of the die pad to its original position which means includes an adjustable regulator for controlling the time interval of movement of the die pad from the retracted to the extended position.

The control means or valve 30 for regulating the flow from the accumulator 14 to the cylinder 12 is moved to the second or operating position wherein unrestricted fluid flow is provided in the second fluid path 26. In the illustrated embodiment, a pressurized fluid source 40 such as air, is adapted to selectively supply fluid pressure to the chamber 42 of control valve 26 to move the piston 44 leftward, as viewed in the drawing, thereby moving the valve body 32 against the action of the spring 34. Conduits 46 and 48 and time delay means 50 provide a fluid flow path 60 between the air pressure source 40 and the chamber 42.

A two position normally closed valve 52 is disposed in the flow path to control the fluid flow between the source and the control member 30. The valve 52 is moved to an operated position connecting the air source to conduit 46 by a cam element 54 carried by the die pad 21 engaging an actuator 56 carried on the valve body. The valve body may be moved to the second operated position by a solenoid 58 actuated at a predetermined position on the return stroke of the ram 20 or by a spring (not shown) to place the conduit in communication with the ambient atmosphere.

The time delay means 50 disposed in the fluid flow path between the conduits 46, 48 includes a flow control element 62 in a valve body 61 and normally urged to a first position by a spring 64 to block fluid flow in the path 60. The flow control element 62 is in the form of a check valve which is guided for movement between open and closed positions on a rod 66 disposed in the flow path 60. One end of the rod 66 is disposed in a chamber 68 disposed below check valve 62 with a piston 63 slidable on the rod and having one surface 63a contacting the check valve 62 and an opposed surface 63b communicating with the chamber 68.

Means are provided for selectively placing the fluid flow path 60 in communication with the chamber 68. In the illustrated embodiment, this means includes branch flow path defined by an axial opening 70 extending through the rod 66 and having one end in open communication with the chamber 68. The opposite end of the opening 70 communicates through a radial port 74 with a passage 72 formed in the valve body which is in direct communication with the flow path 60. Preferably, a filter 76 and a ball valve 78 are disposed in the opening 72 with the ball valve providing unidirectional flow from the flow path to the chamber 68.

Thus, when the conduit 46 is placed in communication with the pressure source 40 the pressure of the fluid on the check valve or flow control element 62 will lock the element in the closed position to prevent fluid flow to the conduit 48. However, a restricted fluid flow is provided to the chamber 68 via opening 70, passage 72 and radial port 74. Once the pressure in the chamber 68 reaches a predetermined level, the pressure on the piston surface 63a will move the piston upwardly carrying the flow control element to the open position.

Preferably, the flow control element is moved from the closed position to the open position as rapidly as possible so as to either completely block the flow in the path 60 or allow substantially unrestricted flow in the path 60. For this purpose, means are provided for varying the surface area 63b subjected to fluid pressure in the chamber 68. In the illustrated embodiment, this means includes an integral fixer member 80 formed in the chamber 68 which contacts a major portion of the piston surface 63b when the piston 63 and the flow control element 62 are in the closed position. This will substantially restrict the surface area subjected to fluid pressure when the piston is in the closed position. However, once the pressure in the chamber 68 has reached a predetermined level, the piston 63 starts to move upward carrying the flow control element 62 with it. Any movement of the piston will subject the entire surface 63b to pressure in the chamber and will thus rapidly move the piston to the second position carrying the flow control element to the open position.

According to another aspect of the invention, regulating means are provided for varying the time interval required to build up sufficient pressure in the chamber 68 to start movement of the piston 63. In the illustrated embodiment, the regulating or adjusting means includes a metering member threadedly received on the upper end of the rod or tube 66. The regulating member 90 is readily rotated on the tube by a control knob 92. Thus, by turning the control knob in a first direction the effective area of the radial port interconnecting opening 70 and 72 can be varied to thereby produce a variable orifice defined by the radial port.

Means are provided for blocking the flow to the chamber 68 whenever the fluid pressure in the conduit 48 is greater than the fluid pressure in the conduit 46. In the illustrated embodiment, this means includes a bore formed in the valve body 61 having one end in communication with the passage or opening 72. A piston 102 is slidably received in the bore 100 and has a first surface in communication with the flow path 60 and a second surface adjacent the end of the bore in communication with the opening 72. Thus, whenever the pressure in conduit 48 is greater than the pressure in conduit 46 the piston 102 will move rightward, as viewed in the drawing, to block the flow between the conduit 46 and the chamber 68.

Also, means are provided for placing the chamber in direct communication with the ambient atmosphere to relieve the pressure build up in the chamber during the time delay period and to purge the chamber of any contaminants which may have accumulated therein. This means includes a conduit or opening formed in the valve body 61 which has one end in comunication with the chamber and the opposite end placed in direct communication with the ambient atmosphere. A tubular extension 112 is provided adjacent the end of the opening in the chamber 68 and a bore 114 is formed in the valve body with one end in communication with the conduit or opening 110 and the opposite end in communication with the flow path 60. A piston 116 is slidably disposed in the bore to be moved from the position shown in the drawing to block the opening 110. However, whenever the pressure in the chamber 68 is greater than the pressure in the conduit 46, the piston 116 will be forced rightwardly, as viewed in the drawing, and place the chamber 68 in direct communication with the ambient atmosphere to reduce the pressure in the chamber and allow the piston 63 and the check valve 62 to be moved to its first position by the spring-64. Of course, the ball valve 78 will be [forced to the closed position to block fluid flow from the conduit 46 to the chamber 68.

Operation [In the starting condition, the die elements are in the open position as shown in the drawing and the die pad 21 is inthe extended position with the piston 12 in the upward position. As the upper die element is forced downwardly during the work stroke of the press ram, the die elements are forced into contact with each other and the hydraulic fluid in the cylinder 12 is passed through the conduit 16, the variable discharge flow path 24 and the line 18 to the accumulator 14. As the die pad 21 descends, the cam 54 moves the valve to place the air pressure source 40 in communication with the conduit 46. The air pressure in conduit 46 will force the piston 116 to the position shown in the drawing. However, a restricted amount of air will pass through the passage 72, the radial port 74 and the axial opening 70 into the chamber 68.

When a suificient pressure buildup is present in the chamber 68, determined by the pressure in the conduit 46 and the setting of the regulator member 90 controlling the size of the radial port, the piston 63 is moved from the first position shown in the drawing forcing the flow control element against the action of the spring 64. After being moved from the first position, the entire surface 63b of the piston 63 is subjected to the pressure in chamber 68 and the flow control valve is snapped open to allow free flow of air to the conduit 48 into the chamber 42 to move the 'valve body 30 and open the second flow path 26 in control valve 10. This will allow substantially unrestricted flow from the accumulator 14 to the cylinder 12 to return the die pad 21 to its extended position.

When the die pad has reached the extended position, shown in the drawing or, the force of a spring (not shown) or the solenoid 58 will move the valve 52 to place conduit 46 in communication with the exhaust conduit allowing the air pressure in chamber 42 to be rapidly exhausted to the atmosphere.

Of course, once the conduit 46 is connected to exhaust, the piston 116 is moved because the pressure in chamber 68 is locked therein and the conduit 110 will place the chamber 68 in communication with the atmosphere. Also, the passage from conduit 48 to chamber 68 will be blocked by both the ball valve 78 and the piston 102 since the pressure in conduit 48 and chamber 68 will be greater than the pressure in conduit 46. Thus, the control element 62 is moved to the closed position by spring 64 which is designed to close only after the spring 34 has moved valve body 32 to the closed position.

As can readily be appreciated, the invention provides a simple mechanical arrangement for delaying the movement of the die pad of a ram-type press from the retracted to the extended position. Furthermore, the period of time delay between pressurization of the conduit and actuation of the control valve is infinitely variable between certain limits by merely turning the control knob 92 in the appropriate direction.

While a preferred embodiment of the invention has been shown and described, it will be understood that various changes and modifications may be made without depart-.

ing from the spirit of the invention as defined by the following claims.

I claim:

1. In a control system for a ram-type press movable between open and closed positions and a die pad which engages the work and is moved between retracted and extended positions by hydraulic means including a hydraulic actuated cylinder and piston, an accumulator tank, a first unidirectional flow path providing restricted flow from said cylinder to said tank, and a second flow path between said cylinder and tank; the improvement comprising biased control means normally urged to a first position wherein the second flow path is blocked and movable to a second position wherein the second flow path allows unrestricted flow between the tank and cylinder to move said die pad to an extended position, means for moving said control means to the second position including a fluid pressure source, valve and conduit means for selectively connecting said source to said control means, and time delay means in said conduit means regulating the movement of said control means to the second position, said time delay means including normally closed valve means blocking fluid flow in said-conduit means, a chamber communicating with said normally closed valve means, a branch path between said valve and conduit means and said chamber whereby a predetermined amount of flow through said branch path will open said normally closed valve means allowing unrestricted flow to open said control means and move the die pad to the extended position.

2. A control system as defined in claim 1, further including an adjustable regulator in said branch path for controlling the flow in the branch path to thereby regulate the time interval of said die pad from the retracted to the extended position.

3. A control system as defined in claim 1, wherein said normally closed valve means includes a normally closed check valve in said valve and conduit means, a piston contacting said check valve and communicating with said chamber for moving said check valve between closed and open positions, means in said chamber defining a first area on said piston subjected to fluid pressure when said piston is in a first position and a second area greater than said first area when said piston is moved from said first position whereby said piston and check valve will rapidly move from the closed to the open position when the pressure in said chamber reaches a predetermined pressure level.

4. In a cycling ram-type press movable between open and closed positions and wherein a die pad engages the work and is retracted upon the closing of the press ram with a hydraulic control system coupled with said press including a cylinder and piston reacting upon said die pad to resist retraction thereof and to return the die pad to its extended position after opening of the press ram, an accumulator coupled with said cylinder, and first and second hydraulic flow paths between said cylinder and accumulator, the improvement comprising means in one of said paths for providing unidirectional restricted flow between said accumulator and cylinder during the work portion of said cycle, first valve means in said second path normally urged to the closed position blocking the flow in either direction, and control means for opening said first valve in response to retraction of said die pad, said control means including a fluid pressure source, a fluid flow path between said source and said first valve means, means responsive to retraction of said die pad to condition said fluid flow path for fluid flow between said source and said first valve means, and means in said fluid flow path delaying the flow of fluid from said source to said first valve means, said delaying means including a normally closed flow control element in said fluid flow path, a piston for moving said flow control element between closed and open positions, a fluid chamber communicating with said flow path and a surface area of said piston, and means restricting fluid flow from said flow path to said chamber whereby said flow control element remains closed until the pressure in said chamber reaches a predetermined level, thereby providing a delay in the return of the die pad to the extended position.

5. A ram-type press as defined in claim 4, in which said chamber includes means for restricting the surface area of said piston subjected to fluid pressure in said chamber when said flow control element is in the closed position and subjecting the entire surface area to fluid pressure when said element and piston are moved from said closed position whereby the fluid pressure in said chamber will rapidly move said flow control element to the open posi tion after the pressure in the chamber reaches the predetermined level.

6. A device asdefined in claim 4, further including means for placing said chamber in direct communication with surrounding ambient atmosphere during a portion of each press cycle to thereby purge said chamber during each cycle.

References Cited UNITED STATES PATENTS Re. 25,027 8/1961 Williamson 267-1 2,890,669 6/ 1959 Williamson 267-1 Williamson 267-1 Williamson 267-1 Williamson 267-1 Perrone 72-351 Perrone 72-351 CHARLES W. LANHAM, Primary Examiner. A. RUDERMAN, Assistant Examiner.

US. Cl. X.R. 

